1. Field of the Invention
The present invention relates generally to the field of respirator masks.
2. Description of the Background Art
A respirator mask is a device used to deliver a gas or gases to a patient. In its simplest form, the respirator mask includes a face piece, headgear for attaching the face piece to the head of the patient, and a gas supply hose. The respirator mask can be used to deliver a variety of gases, including air or oxygen, and a variety of medicines or treatments.
In recent years, respirator masks have been used in the treatment of obstructive sleep apnea and other respiratory illnesses. Treatment of obstructive sleep apnea using a respirator mask is known as continuous positive airway pressure (CPAP) therapy. The therapy is typically administered at night while the patient is asleep and involves placing a respirator mask over the nose and mouth of the patient during sleep. Positive air pressure from an air compressor or blower is forced through the respirator mask into the patient""s airway via the nasal passages to keep the airway open.
An impediment to effective CPAP therapy is the occurrence of air leakage between the skin and the mask seal. Even very small leaks can be perceived by the wearer, who then compensates by increasing the pressure of the mask against the face. While reducing leakage, this action may cause skin irritation and injury. In either case, sleep is interrupted, putting the effectiveness of the therapy at risk.
A variety of mask seals have been developed to improve patient comfort by reducing leakage from the mask. One type of respirator mask, exemplified by U.S. Pat. Nos. 4,907,584, 4,971,051, and 5,540,223, relies on direct compression of an elastomeric cushion against the skin to form a primary seal. Another type of respirator mask, exemplified by U.S. Pat. Nos. 5,243,971, 5,655,527, and 4,167,185, relies on a xe2x80x9creverse flapxe2x80x9d that is held against the skin by the internal air pressure of the mask. In both types of mask, a single seal of varying area stands between the high-pressure air inside the mask and the outside atmosphere. Inevitably, the fit of such masks is not perfect, and the patient must compensate for any fitting inaccuracy by tightening the headgear that is used to attach the mask to the head of the wearer. The result is either leakage or painful pressure points against the skin.
Yet another type of respirator mask, exemplified by U.S. Pat. No. 4,739,755, utilizes a seal with multiple edges to enhance sealing efficiency. In this type of mask, both seal edges are approximately conterminous, extending about the nose with approximately the same perimeter. Thus, inaccuracies in fit are likely to affect both edges.
There remains a need in the art for an improved respirator mask.
A respirator mask is provided according to a first aspect of the present invention. The respirator mask includes an inner plenum with a gas inlet and a manifold adapted to fit under the nose of a patient, a pair of nasal inserts projecting from apertures in the manifold to define primary seals with the nasal passages of the patient, an outer plenum adapted to surround at least the nose of the patient, a secondary seal mounted on an outer edge of the outer plenum and adapted to contact the face of the patient around the nose in air tight relation, and at least one opening formed in the inner plenum to permit gas to flow from the inner plenum into the outer plenum. By pressurizing the outer plenum, the mask of the present invention decreases the pressure differential between the interior of the mask and the outside atmosphere to reduce the gas flow rate out of the mask in the event of a leak. Diversion of gas into the outer plenum also allows use of an inflatable secondary seal to maintain air-tight contact with the face of the user.
A method of treating a respiratory ailment is provided according to a second aspect of the present invention. The method includes connecting a source of pressurized gas to an inner plenum of a respirator mask having an outer plenum configured to cover only the nose of a patient, mounting the respirator mask to the face of a patient over the patient""s nose such that nasal inserts carried by the inner plenum form substantially air-tight primary seals with the patient""s nasal passages and the outer plenum forms a substantially air-tight secondary seal around the patient""s nose, and activating the source of pressurized gas to supply positive gas pressure to the mask, wherein a portion of the pressurized gas is permitted to flow from the inner plenum to the outer plenum via an opening to create a region of intermediate pressure between the primary and secondary seals.
The above and other features and advantages of the present invention will be further understood from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings wherein like elements are referred to using the same reference numerals.